The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
When an engine of a vehicle stops after the vehicle has been driven, coolant in a turbocharger is vaporized and discharged therefrom, and thus the turbocharger is maintained in a high-temperature state.
FIG. 1 is a block diagram showing a coolant circulation system for a turbocharger according to a conventional technique. When the ignition of a vehicle is turned off while a turbocharger 500 is in a high-temperature state, coolant is continuously drawn into the turbocharger 500 that is in the high-temperature state, so that a large amount of vapor generated by a coolant boiling phenomenon is transmitted to a heater core 510. Thereby, boundary noise is generated by contact between liquefied coolant and gaseous coolant in the heater core 510.
Furthermore, when a large amount of vapor is supplied to a radiator cap 530, an overflow phenomenon is caused, whereby noise is generated from a reservoir tank 540.
In an effort to overcome the problem of noise, a conventional technique was proposed, in which an additional electric water pump is provided so that even after the ignition of the vehicle is turned off, coolant is continuously supplied to a turbocharger for a predetermined time so as to reduce the temperature of a bearing housing and thus prevent a coolant boiling phenomenon.
However, this conventional technique is problematic in that the production cost and the weight increase because the additional electric water pump is required.